1. Field of the Invention
The present invention relates to mounting structures for fans, and particularly to mounting structures for isolating engine fans from engine vibration.
2. Description of the Related Art
Engines with an odd number of cylinders, and particularly 3-cylinder engines, are prone to vibrate in a manner which causes the axis of their drive shaft to pitch and yaw. This can pose problems for the cooling fan for the engine, since the angular momentum of the rotating fan tends to resist changes to the direction of the fan axis. In extreme cases, the fan blades may even break off from metal fatigue.
The center of a typical engine fan is co-axial with a drive shaft, e.g., for the engine water pump, mounted to the engine. A pulley or fan spacer typically is mounted to the end of the drive shaft, and the fan is piloted on the shaft or a concentric spud and bolted to the pulley with a plurality of bolts spaced around the axis of the shaft. When mounted in this manner, all vibrations in the shaft and pulley are transmitted directly to the fan.
U.S. Pat. Nos. 3,757,914 (Elmer), 3,893,555 (Elmer) and 4,682,679 (Elmer) all teach structures for isolating a fan against the torsional vibrations which may arise when using a viscous drive or other thermal clutch in connection with a cooling fan. However, these references do not address the problem of isolating the fan against pitch and yaw vibrations.